DC current breaking capabilities of an EHV CB 3

[protkid1]

Hi friends,
I have a 275 kV SF6 CB having the following rating :
Rated short time withstand : 40 kA
Rated peak withstand : 100 kA
Rated making current : 100 kAp
Rated breaking current asymmetrical : 40 kA
Out of phase breaking current: 10 kA
First pole to clear factor : 1.5
Transient recovery voltage : 249
Rated line charging breaking current : 50 A

http://www.eng-tips.com/

Rated cable charging breaking current : 160 A
Rated Back to back capacitor bank breaking current : 400 A

Rated reactor current breaking : Max 315 A/ min 41 A
Max overvoltage factor on any switching duty : 2.3 p.u.

Total break time: 33 ms.

1) I want to know whether the above CB can break a DC current of 500 A ? The application is for switching in a shunt reactor feeding a 100 km long transmission cable. Sywitching studies indicate a 500 A dc persisting for 1.5 sec upon energisation of the shunt reactor.
2) Is it recommended to use the above CB for breaking a purely capacitive current of approx. 250 A ?
Thanks
protkid

 

[protkid1]

Dear friends,
I need in urgent info. The factor of 2.3 p.u stated as "the overvoltage factor during any of the above switching duties" as per IEC is under question. The manufacturer has type test reports to prove that the 132 kV rated CB can break a capacitive current of 656 A r.m.s with a prospective TRV of 329 kV peak (done by synthetic test,test duty 2 BC2). Now we require the CB to break only 250 A. But we do not have reference to prove that the overvoltage factor of 2.3 p.u will not be violated when this CB breaks 250 A capacitive. My question is :

Is it possible to extrapolate or derive the TRV for 250 A case from the 656 A type test report ?

The report says:
Uc (kV peak) 329 kV
U1 (kV peak) less than 11.6 kV, t1 = 58 micro sec t2 = 7.3 ms. ( 4 point TRV expression ?)

I am proceeding to read IEC 62271-100 to find out about the same.

Thanks